I debox all my non-LE dolls and some of my LE dolls (and haven't decided about the others yet). I do keep the boxes for my LE dolls though.
I don't regret it because I bought them specifically for my enjoyment. Many of the times, the doll can't be fully appreciated in the box, like the detail on the back can't be seen, the skirt is compressed, the shoes can't be enjoyed. I also like to swap and sometimes modify clothing for similarly sized dolls to create new looks, and create dioramas.
With some of the LE dolls, they are nicely displayed in the box and I don't feel a real urge to open them (yet). Disney does better in this department than Barbie, IMO. (Then again, Barbie LE comes in a thick outer box-box that protects the inner box, so in that way they're more thoughtful to collectors. I guess every company has its pros and cons).